International Rhinologic Society Rhinology 0300-0729 2026 05 21 Economic analysis of surgery and biological therapy for chronic rhinosinusitis with nasal polyps EN J. Maza-SolanoRhinology and Skull Base Unit, Department of Otolaryngology, University Hospital Virgen del Rocío, Seville, Spain Department of Surgery, University of Seville, Seville, Spain L. García-MochónBiomedical Research Center at Ciber for Epidemiology and Public Health (CIBERESP by its Spanish acronym), Madrid, Spain IBS Biomedical Research Institute, Granada, Spain Department of Applied Economics, University of Granada, University Campus of Cartuja s/n, Granada, Spain J. Martín-Martín Department of Applied Economics, University of Granada, University Campus of Cartuja s/n, Granada, Spain P.W. HellingsDept Otorhinolaryngology, University of Leuven, Belgium Laboratory of Allergy and Clinical Immunology, University of Leuven, Belgium Upper Airways Research Group, University of Ghent, Belgium S. Sánchez-GomezDepartment of Surgery, University of Seville, Seville, Spain Rhinology and Skull Base Unit, Department of Otolaryngology, University Hospital Virgen Macarena, Seville, Spain Journal Article 3466 10.4193/Rhin25.529 Background: Chronic rhinosinusitis with nasal polyps (CRSwNP) imposes major health and economic burdens. Endoscopic sinus surgery (ESS) and biologic therapy are treatment options. This study compares their effectiveness and cost-efficiency from the Spanish National Health System (NHS) perspective. Methodology: An economic evaluation was conducted in severe CRSwNP, following Spanish-NHS guidelines. Data came from a tertiary-hospital with 10-year projections. Effectiveness was measured as reduction in the Sinonasal Outcome Test-22 (SNOT-22). Cost-utility analysis used quality-adjusted life years (QALYs). Micro-costing was applied for ESS, while annual drug costs were considered for biologics. Sensitivity analyses tested robustness. Results: 89 patients were included (63 ESS, 26 biologics). After 2-years, both strategies achieved similar SNOT-22 improvements (-31.8 ESS, -31.0 biologics). Costs were far lower for ESS (€5,302.78) than biologics (€27,198.23), making biologics less efficient despite comparable benefit. The 2-year incremental cost-utility ratio (ICUR) for biologics was €1.2 million/QALY, above accepted thresholds. At 10-years, biologics yielded 2.75 QALYs at an incremental cost of €108,917.62 (ICUR €39,592/QALY). Sensitivity ana-lyses showed that biologics generally remained above commonly accepted willingness-to-pay thresholds, although substantial price reductions (up to 40%) allowed ICURs to approach the upper limit of acceptability. Conclusions: Both treatments provide meaningful improvement. ESS remained the less costly strategy and was more efficient over the short term, whereas long-term projections showed higher QALY gains with biologics at substantially greater cost. Within Spanish- NHS, biologics may approach cost-effectiveness only under favorable pricing assumptions and should be reserved for patients with contraindications or persistent disease after ESS.